A problem associated with distributed networks and wide area communications systems is the difficulty of performing a closed-loop test of the transmission paths. A closed-loop test is defined as a test which can verify the operation of a transmission path from point A to point B and also from point B to point A. In a distributed network, where point A and point B may be separated by a significant distance, performing a closed-loop test can be especially difficult. One method to perform a closed-loop test is to place a first individual at point A and a second individual at point B. By coordinating their efforts, a signal can be injected into the transmission path at point A by the first individual and the reception can be verified by the second individual at point B. In response, the method can be repeated from point B to point A. Another method to perform a closed-loop test is to provide a loop-back at point B. With a loop-back in place, a signal transmitted from point A will reach point B and then continue back to point A if the transmission paths are operational. Loop-back testing is often utilized in testing systems that are off-line; however, in a live telecommunications system such as the public switched telephone network (PSTN), the use of a loop-back test is impractical.
The public switched telephone network is an example of a telecommunications system which requires a closed-loop testing capability for the various transmission paths. In servicing customers, a telephone service technician may need to verify the operation of a subscriber line or a piece or plurality of pieces of terminating equipment attached to a subscriber line. In the past, this verification has been accomplished by placing a call to a service operator to verify the ability to place an outgoing call from the piece of terminating equipment and/or subscriber line (i.e. point A to point B verification). In addition, the service technician could request the service operator to place a call to the piece of terminating equipment and/or subscriber line under test to verify the ability to receive an incoming call (i.e. point B to point A verification). However, due to the size and complexity of the PSTN, closed-loop testing in this manner is impractical. Thus, there is a need for system and a method to provide a closed-loop test capability for a service technician attempting to verify the operation of a subscriber line or terminating equipment attached to a subscriber line.
Several closed-loop testing techniques have been developed to address this need. One technique is provided within automatic number announcement circuits (ANAC). The ANAC technique consists of a box which can be functionally connected to a central office by means of a dedicated line. In operation, a service technician uses the terminating equipment and/or subscriber line under test to dial a directory number associated with the ANAC's dedicated line. The call is then directed to the ANAC by the central office. The directory number of the subscriber line under test is provided to the ANAC through a service such as calling line identification or some other means. The ANAC converts the directory number of the subscriber line under test into an audio signal and then transmits the audio signal over the transmission path back to the subscriber line under test. Reception of the audio signal at the terminating equipment and/or subscriber line under test verifies the ability to receive audio over the transmission path. The ANAC technique provides the capability to verify that a subscriber line can place outgoing calls and receive audio signals. Further, to provide a full, closed-loop test capability, additional features are necessary to verify the ability to receive calls and transmit audio.
The development of the call-back test system has also addressed, in part, the need for closed-loop testing of subscriber lines. Similar to ANAC's, a call-back test system is connected to a central office by means of a dedicated line having a unique directory number. In operation, a service technician uses the terminating equipment and/or subscriber line under test to dial the unique directory number of the call-back test system. The call is directed to the call-back test system by the central office. The directory number associated with the subscriber line under test is provided to the call-back test system by the central office. After receiving the directory number at the subscriber line under test, the call is then ended. Next, the call-back test system initiates a call to the directory number of the subscriber line under test. Upon detecting an answer to the call, the call-back test system can transmit an audio signal to the subscriber line under test. Reception of the audio signal at the terminating equipment and/or subscriber line under test verifies the ability to receive audio signals. The call back system provides the capability to verify that a subscriber line can place outgoing calls, receive incoming calls and receive an audio signal.
Other systems have been introduced to provide closed-loop testing of transmission paths. These systems include ANAC devices with call-back capabilities and call-back facsimile machines. There are at least two limitations that exist in each of the previous systems. First, the previous systems are central office oriented. This is limiting because duplicate equipment must be purchased for each central office or at least for one central office within each area code. Furthermore, to test subscriber lines which do not have local access to a test system, long-distance calls must be placed to a central office equipped with a test system. The costs associated with long-distance testing of subscriber lines can be significant. Thus, there is a need for a testing system which is accessible from any subscriber line or piece of terminating equipment within a telecommunications system. There is also a need for a toll-free testing system which is accessible from any subscriber line or piece of terminating equipment within a telecommunications system.
Second, the referenced systems do not offer the capability to verify multiple functions of the subscriber line and/or terminating equipment. Today, it is common for a single subscriber line to serve multiple functions. For instance, a subscriber line may be used for receiving telephone calls and for receiving facsimile transmissions. In addition, calling line identification equipment may be either attached to the subscriber line or incorporated into the terminating equipment. Testing each of the functions of a subscriber line being used for multiple purposes (i.e., facsimile, voice, calling line identification, etc.) can be complex. For instance, a service technician is required to call a first number to test one function. Upon completion of this test, the service technician must call a second number to test a second function, and so on. The service technician must maintain a list of the various test numbers and the test functions provided by each. In addition, having a unique directory number for each test system is an inefficient utilization of directory numbers. Thus, there is a need for a service platform which can provide multiple test functions and be accessed by a single directory number.
A service feature which facilitates the ability to test terminating equipment and/or subscriber lines is calling line identification (CLID). CLID is a feature which provides the recipient of an incoming call with information regarding the source or origin of the incoming call. When an incoming call is received on a subscriber line having CLID equipment attached, the CLID equipment detects and decodes a CLID signal. After decoding the signal, the identity of the originating line can be displayed on the equipment or audibly announced. Generally, the identity of the originating line consists of the directory number assigned to the originating subscriber line.
A feature related to calling line identification is dialed number privacy or DN privacy. The DN privacy feature allows an originator of a call to block the transmission of the CLID signal to the called subscriber line. Typically, the DN privacy feature can be activated or de-activated for a given subscriber line by a user dialing a special sequence on a piece of terminating equipment attached to the subscriber line. When the DN privacy feature for an originating subscriber line is in the active state, the signal which provides the calling line identification of the subscriber line is blocked from being transmitted to the called subscriber line. Thus, when active, the DN privacy feature can prevent a call-back test system from being able to verify the operation of a subscriber line or attached terminating equipment. For instance, a call-back test system is usually dependent upon receiving the calling line identification of the subscriber line under test in order to initiate the call-back call. When the transmission of the CLID signal is blocked, the call-back test system can not determine the directory number of the subscriber line under test, and hence, cannot initiate the call-back call. Furthermore, there is generally no mechanism, either visual or audible, which serves to indicate the state of the DN privacy feature for a subscriber line. Thus, if the DN privacy feature is active, a service technician attempting a call-back test may erroneously identify the subscriber line as inoperable to receive calls. Therefore, there is a need for a test system which can determine when the DN privacy feature is active and notify a party or service technician that further testing can not be performed unless the DN privacy feature is turned off.